This invention relates generally to measuring methods and apparatus for measuring, and is more particularly directed to the measurement of the relative amounts of a first and second liquid, where one liquid is held up or suspended in a liquid/liquid dispersed phase system. The invention is also directed to a system in which the travel time of ultrasonic pulses through the liquid/liquid dispersion is employed to derive the fractional volumetric dispersed phase holdup of the two-liquid dispersed phase system.
The present invention is more closely related to self-calibrated continuous monitoring of the dispersed phase fractional volumetric holdup, and to the continuous monitoring of the separate liquid phases, which can, and are expected to, change chemically during the time that the liquids are being monitored.
The invention can be applied to liquid-liquid extractors of the types known as pulsed columns, vibrating plate columns, rotating disc contactors, multi-state stirred columns, Kunii columns, mixer-settlers, and a variety of other liquid-liquid extractors and processing vessels. The invention can be applied to tubular reactors with or without internal means to sustain primary dispersions through turbulent mixing.
Previously, the measurement of the dispersed phase fractional volumetric holdup in two-phase liquid systems has been attempted by such techniques as displacement, pressure differentials, direct sampling, light beam attenuation, and electroresistivity. While these approaches can be employed to derive a result, none of them permits estimation or monitoring of the dispersed phase fractional volumetric holdup under steady state process conditions or during transient conditions. Additionally, none of these techniques can be considered non-invasive or non-intrusive. Consequently, none has proved entirely effective for monitoring the dispersed phase fractional volumetric holdup for liquids within a reaction vessel.
The dispersed-phase fractional holdup is an important parameter in calculations of the efficacy of a chemical reaction or mass transfer in multi-phase liquids, as it corresponds to the relative mass transfer interfacial area in a two-phase liquid system. Real-time accurate knowledge of this quantity permits optimization of liquid flow rates to carry out the chemical reaction with minimal waste and consistent product.
Therefore, it would be desirable to achieve accurate, non-invasive, non-intrusive, on-line continuous measurement of this parameter, thereby permitting optimization of liquid flow rates to conduct the chemical reaction or mass transfer with minimal waste. Accurate knowledge of dispersed phase fractional holdup would also permit optimal direct computerized process control, to produce consistent quality product and maintain safety of operation.
One previous approach to ultrasonic measurement of this quantity employed a sound velocimeter that was immersed in the liquid/liquid dispersion. This technique had the drawback of interfering with the flow of liquids through the reactor vessel.
No previous technique provided for self-calibration by directly measuring the properties of the pure liquid phases during the ongoing process to establish optimal steady-state conditions.